(a) Technical Field
The present disclosure relates to a thin film transistor array panel, a method for manufacturing the same, and a liquid crystal display.
(b) Discussion of Related Art
Flat panel displays are thin as compared to conventional cathode ray tube (CRT) displays. Examples of flat panel displays include a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting device (OLED).
The LCD is a display device using electro-optical characteristics of liquid crystals in which light transmission amounts are varied according to the intensity of an applied electric field to thereby realize the display of images. The PDP is a display device for displaying images by using plasma generated by gas discharge. In the OLED, electrons and holes are injected into an organic illumination layer respectively from a cathode (e.g., the electron injection electrode) and an anode (e.g., the hole injection electrode). The injected electrons and holes are combined to generate excitons, which illuminate when transitioning from an excited state to a ground state.
In an active matrix type flat panel display, each pixel may be independently controlled by including switching elements such as thin film transistors. The thin film transistors and a color filter may be formed on a same substrate, which is referred to as “color filter on array” (COA). A capping layer may be formed on the color filter in the COA structure. The capping layer prevents the color filter from lifting by blocking the generation of outgassing from the color filter, thereby reducing image deterioration due to artifacts such as residual images when the display is driven. The color filter may be made of an organic material with some elasticity. The capping layer may be made of an inorganic material with a smaller elasticity and compressibility as compared with the color filter of the organic layer.
However, when the solid capping layer is formed on the soft color filter, stress is generated on the capping layer. Further, the capping layer and the color filter have different compressibility and elasticity, such that a lifting is generated in the interface surface thereof. For example, when contacting a spacer on the capping layer in a liquid crystal display, the compressibility of the contact portion is decreased. Therefore, the margins of the liquid crystal are reduced, and as a result, active unfilled area (AUA) deterioration is generated due to insufficient liquid crystal in some portions of the display area. An example of AUA deterioration generated according to the stress of the capping layer is shown in the graph of FIG. 7.